As illustrated in FIGS. 8 and 9, Patent Document 1 discloses a light-conducting apparatus 1 including a single light source 2 and a light-conducting member 3. The light-conducting member 3 includes a ring-shaped portion 3a and a tangentially extending portion 3c located radially outside the ring-shaped portion 3a and extending in a tangential direction of the ring-shaped portion 3a from the ring-shaped portion 3a. The ring-shaped portion 3a extends continuously over an entire circumference of the ring-shaped portion in a circumferential direction of the ring-shaped portion. The tangentially extending portion 3c causes light having entered the light-conducting member 3 through a light-receiving surface 3b to enter the ring-shaped portion 3a in an only one direction D in the circumferential direction of the ring-shaped portion 3a. 
The light having entered the ring-shaped portion 3a in the one direction D is totally reflected at a radially outside boundary surface of the ring-shaped portion 3a between the ring-shaped portion 3a and air outside the ring-shaped portion 3a, and travels in the ring-shaped portion 3a in the one direction D. The light having entered the ring-shaped portion 3a is diffused at a radially inner surface 3d of the ring-shaped portion 3a which is surface-treated. Therefore, the ring-shaped portion 3a illuminates in a shape of a ring.